There are a number of industrial processes that require a supply of chilled water or other liquid coolant that maintains the industrial process within predetermined thermal limits. The water chiller is often a stand-alone device, complete in and of itself, with appropriate supply and return connections for conduits connected to the industrial process. The industrial process may be an injection molding machine for molding plastic devices; a number of other industrial processes have similar requirements. As with any industrial equipment, cost may be an important factor for the chiller.
In recent years, particularly with thee advent of electrical discharge machining (EDM) equipment, it has been necessary to provide de-ionized water as the liquid coolant. The usual electrical conductivity of water that is not thoroughly de-ionized cannot be tolerated. Conventional metal fittings are undesirable because continued use of fittings of this kind, in the chiller, may lead to degradation of the initially de-ionized water to the extent that ineffective operation may result. As a consequence, the bypass conduit in the chiller has frequently been made of stainless steel. There is usually a valve in the bypass line; the result is that the complete bypass, which is a necessity in order to avoid freeze-up and/or overheating of the chilling apparatus, and to avoid pump damage, becomes unduly expensive. This is particularly true in instances in which the bypass and other internal coolant circuits in the chiller are formed of stainless steel.